R² + 7 r + 10 = r² + 2 r + 5 r + 10 = r ( r + 2 ) + 5 ( r + 2 ) = ( r + 2 ) ( r + 5 )
r² - 5 r - 50 = r² - 10 r + 5 r - 50 = r ( r - 10 ) + 5 ( r - 10 ) = ( r - 10 ) ( r + 5 )
![\frac{r^{2} +7r+10}{3}* \frac{3r-30}{r ^{2}-5r-50 }= \\ \frac{(r+5)(r+2)}{3}* \frac{3(r-10)}{(r-10)(r+5)}](https://tex.z-dn.net/?f=%20%5Cfrac%7Br%5E%7B2%7D%20%2B7r%2B10%7D%7B3%7D%2A%20%5Cfrac%7B3r-30%7D%7Br%20%5E%7B2%7D-5r-50%20%7D%3D%20%5C%5C%20%20%5Cfrac%7B%28r%2B5%29%28r%2B2%29%7D%7B3%7D%2A%20%5Cfrac%7B3%28r-10%29%7D%7B%28r-10%29%28r%2B5%29%7D%20%20%20%20)
= ( after cancellation ) =
r + 2
I think they mean how to make it an improper fraction. My guess would be 7 over 1, but I could be wrong.